Front-engine transit bus vehicles are known in the commercial vehicle art. Such vehicles typically have low elevation bodies with the engine and transmission located under the driver and passenger platform, and as a result, present difficulties for engine combustion fresh air induction. Due to the lower vehicle platform elevation and positioning of the driver's platform, cooling module, and passenger entry doors above and around the engine location, it is difficult to access and provide engine fresh air induction. Further, such low elevation and positioning render it difficult to provide the engine with induction air that is not preheated by powertrain heat rejection or that is not susceptible to entrained or directly ingested water.
Current front-engine transit bus air induction systems typically ingest air from beneath the platform. This under-platform air is generally protected from water ingestion but is substantially preheated by heat emanating from the engine and vehicle cooling module. Ingesting such preheated air into the engine air induction system increases turbocharger air inlet temperatures. These high turbo inlet air temperatures can prevent the engine from meeting the engine manufacturer's installation requirements and can prevent the engine installation from qualifying under Environmental Protection Agency (EPA) requirements. These EPA requirements, among other things, control the amount of emissions produced by the engine, and the engine installations in most front-engine buses and other highway vehicles are required to meet these standards.
To attempt to overcome this problem, air intake systems were developed and generally included a “J-shaped” tube that was attached to the vehicle underbody at the engine air cleaner, which feeds the engine via the turbo inlet. Air enters the tube, filters through the air cleaner, and passes into the turbo inlet of the engine. The inlet end of the J-tube is typically defined at a top surface of the tube to prevent water or moisture from entering the tube and damaging the engine.
However, because these previous systems do not provide an interface to external air, they induct overheated under-platform air into the air cleaner. As indicated above, such high temperature intake air can prevent the engine from meeting the manufacturer's installation requirements, thereby preventing the engine installation from complying with EPA emissions requirements.
Front engine bus chassis are typically built as drivable chassis and taken to a separate body plant for body installation or sold as drivable chassis to independent body builders. Accordingly, bus chassis manufacturers wish to manufacture the induction system on the plant's chassis production line, enabling delivery of completed and drivable chassis having a validated engine air intake system to second-party vehicle body builders, ensuring that the engine installation meets the required standards.